Alkylation process and stabilization of product



June 1964 LE ROI E. HUTCHINGS 3,138,645

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ATTORNEY United States Patent 3,138,645 ALKYLATION PROCESS AND STABHJZATION 9F PRDDUCT' Le Roi E. Hutchings, Crystal Lake,.lll., as'signor to The Pure Oil Company, Chicago, Ill., a corporation of flhio Fiied Aug. 21,1961, Ser. No. 132,912 9 Ciairns. (Cl. 260-68351) This invention is directed to the manufacture of paraffinic hydrocarbons boiling in the range of about 49 C. to about 100 C. at 760 mm. Hg, i.e., in the hexane and heptane boiling range, which paraffinic hydrocarbons have a low content of benzene and other aromatic hydrocarbons. More particularly, this invention relates to a meth- 0d of preparing hexane or hexane-containing fractions (commercial hexane), or C C hydrocarbon fractions of low benzene (or other aromatic hydrocarbon) content, by conventionally reforming a naphtha rich in C -C hydrocarbons, stabilizing the reformate, subjecting the stabilized reformate to conventional solvent extraction to separate an aromatic-rich extract and a paraffin-rich raffinate (containing the parafiins and predominating in hexanes), subjecting the raffinate to alkylation, and fractionating the resulting alkylate to separate a fraction rich in said paraffins, i.e., hexane which has a concentration of aromatics less than about 0.5 by volume. This invention is also directed to preparing heptane or heptane-containing fractions (commercial heptane) containing low concentrations of toluene by the foregoing steps and separating a heptane traction boiling in the range of 75 C. to about 100 C. which is substantially free of toluene (contains less than 0.5% toluene) and to the treatment of a reformate to produce a 49 C.-100 C. fraction, by said steps, from which is produced both a hexane fraction and a heptane fraction, free of benzene and toluene respectively, which qualify as commercial hexane and heptane fractions. This invention is directed particularly to the preparation of substantially pure alkanes, boiling in the range 49 C. to 75 C. at 760 mm. Hg.

Hexane and hexane fractions are used commercially as solvents and as raw materials for the manufacture of var ious chemicals. They frequently are obtained by fractional distillation from petroleum streamswhich also contain benzene. In general, it has been economically possible to obtain hexane fractions containing as little as about 2% v. of benzene by extraction and distillation, but the relatively close boiling points of benzene and hexane have made more complete separation than this impossible. Although hexanes containing more than about 2.0% v. of benzene still are widely marketed, there are indications that the future specification for maximum benzene content in hexanes may be set at 0.5% v. In any event, hexaues containing less than about 0.5% v. of benzene usually can command a higher market price than hexanes containing greater amounts of benzene. The same considerations apply to heptane fractions and their toluene content.

Now, in accordance with this invention, I have devised an integrated process for the preparation of paraflinic hydrocarbon fractions, such as hexanes, containing not more than 0.5 v. of benzene from a naphtha rich in hydrocarbons containing 6 to 8 carbon atoms per molecule. I have also devised an integrated process for the preparation of parafiinic hydrocarbon fractions, such as heptanes, containing no more than about 0.5% v. of toluene from a naphtha rich in hydrocarbons containing 6 to 8 carbon atoms per molecule.

The process of this invention consists of the steps of (l) catalytically reforming a naphtha rich in hydrocarbons containing 6 to 8 carbon atoms per molecule, (2) subjecting the eflluent from the reforming operation to extraction by contact with a selective solvent for aromatice ics, (3) if hydrocarbons of over 8 carbon atoms are present, distilling to recover the desired hydrocarbon fraction in the range C -C this step may be carried out prior to extraction, (4) combining the selected raflinate fraction (i.e., the parafiin-rich fraction) from the extraction step with an alkylatable hydrocarbon mixture, such as isobutane and isobutylene, (5) subjecting the mixture to contact wit-h hydrofluoric or sulfuric acid under alkylation conditions, and (6) fractionally distilling the eifiuent from the alkylation reaction to obtain alkylate, unreacted paraffins, (that is, the isobutane and isobutylene), and a C C hydrocarbon fraction, i.e., a hexane fraction containing less than 0.5 v. of benzene or a heptane fraction containing less than 0.5 v. of toluene, or to obtain both such fractions from a given reformate.

Accordingly, it becomes a primary object of this invention to provide a process for preparing substantially aromatic-free C -C parafiins.

Another object of this invention is to provide a process for preparing commercial hexane having a content of benzene of less than about 0.5% by Volume.

A further object of this invention is to provide a process for preparing commercial heptane having a content of toiuene of less than about 0.5 by volume.

An object of this invention is to provide a process for preparing substantially aromatic-free commercial hexane which comprises catalytically reforming a naphtha, stabilizing the reformate, subjecting the reformate to extraction to recover a raiiinate rich in paraflinic hydrocarbons, combining the parafiin-rich fraction with an iso-parafiinic hydrocarbon and an olefin, subjecting the mixture to acid alkylation, and fractionating the alkylate to recover a fraction consisting of hexane containing less than about 0.5% by volume of benzene.

These and other objects of this invention will be described or become apparent as the specification proceeds.

The drawing is a diagrammatic illustration of the process steps of the invention. Valves, pumps, heat exchangers and other auxiliary equipment which will be obvious to one skilled in this art have been omitted for simplicity.

Naphtha, rich in hydrocarbons containing six carbon atoms per molecule (paraflins and naphthenes), enters through line 10 and flows to catalytic reforming unit 12. Gaseous products are removed from the reformed product (stabilization of the reformate) to prevent their interference with subsequent extraction. This is accomplished by sending the reformate through line 14 to still 16 wherein gaseous products are taken overhead at line 18. Any hydrocarbons above C are taken otf as hottoms at line 20. The stabilized and selected product from reforming unit 12 flows through line 22 to extraction tower 24, wherein it is countercurrently contacted with selective solvent entering through line 26. Rich solvent from tower 24, containing dissolved aromatics, flows through line 28 to stripping tower or still 30, from which aromatics are withdrawn as product through line 32, while lean solvent is withdrawn through line 26 and recycled to extraction tower 24.

Rafiinate from extraction tower 24 flows through line 34 and joins parafiinic hydrocarbon (isobutane) entering through line 36 and olefinic hydrocarbon (isobutylene) entering through line 38.

The mixture then flows through line 40 to alkylation reactor 42, Where it is contacted at alkylation conditions with hydrofluoric or sulfuric acid entering through line 44. Here any benzene is alkylated by a portion of the isobutylene to produce a higher-boiling product during the alkylation of isobutane by isobutylene. Spent acid is Withdrawn from alkylation reactor 42 through line 46, while the alkylated hydrocarbon mixture is withdrawn through line 48, and transferred to fractional distillation A sample of raffinate obtained by selectively extracting aromatics from a catalytic reformate (Udex raflinate from Platformer product) was used along with isobutane and isobutylene in an alkylation run with liquid hydrofiuoric acid as catalyst, to determine whether this treatment would lower the benzene content of the raifinate. Another portion of the raflinate was used in an alkylation run with 98% sulfuric acid as the catalyst. The details and results of the alkylation runs were as follows:

product with 2-hydroxyethyl dimethyl carbamate, is fractionally distilled to obtain about 6.5% of a C -C hydrocarbon fraction predominating in heptane containing about 2.1% of aromatics, principally toluene. A mixture of about 150 cc. of this C C fraction and 100 cc. of 98% sulfuric acid is stirred under atmospheric pressure at about C. while a mixture of equal volumes of isobutane and isobutylene is passed therethrough. While the normal alkylation reaction between the isobutane and isobutylene is progressing, the aromatic content of the mixture is being alkylated by isobutylene to toluene and other alkyl aromatics boiling higher than heptane. The 320 cc. hydrocarbon product resulting from the alkylation is fractionally distilled to give about 38 cc. of a heptanefraction product boiling between 90-100 C. at 760 mm. and containing about 0.24% toluene. This final product is suitable for use as commercial heptane.

EXAMPLE IV A sample of rafiinate boiling up to 230 C., obtained Isobutane-Isobutylene Alkylation in the Presence of Udex Raflinate [Properties of Udex RaiIinate: Gravity 74.8 A.P.I.; A.S.T.M. Distillation F.); IBP 130, 5% 150, 10% 154, 161, 50% 160,

Reaetants Conditions Product Run Udex Raflmate Isobutane Isobutylene Calculated N0. Catalyst Total Benzene Max. Benz. Temp. Press. Yield Content Content of F.) (mm.) (g.) (Vol. Hexane g. moles g. moles g. moles percent) Cut, (Vol.

percent) 1 Li %.(l4lgdr)ofluroic Ac- 131.5 1.4 47 0.8 45 0.8 125 214 0.14 0.50

1 g. 2...... 98%)Sulfuric Acid (400 361 4.0 70 1.2 56 1.0 14-32 atrn approx. 0.13 0.38 470 1 Heated in closed steel bomb for 5 hours. 2 Stirred for 1.5 hours.

The Calculated Maximum Benzene Content (vol. of the Hexane Cut From Alkylation Product was determined on the assumption that the hexane distilled from the alkylation products would contain all of the benzene present. Thus, these values represent the maximum possible benzene concentration in the hexane. In practice, the values probably would be smaller.

It previously had been determined that precise distillation of this raffinate would yield 44.1% v. of hexane containing 2% v. of benzene. Thus, it is apparent that the alkylation carried out in accordance with this invention resulted in a markedly superior product.

EXAMPLE II A sample of raffinate boiling up to 440 F. (227 C.), and obtained by selectively extracting aromatics from a Platformer product with diethylene glycol, is fractionally distilled to obtain 6.1% of a C -C hydrocarbon fraction containing 2.1% benzene. A mixture of 150 cc. of this C -C fraction and 100 cc. of 98% sulfuric acid is stirred under atmospheric pressure at F. C.) while a mixture of equal volumes of isobutane and isobutylene is passed therethrough. While the normal alkylation reaction is occurring with isobutane and isobutylene, much of the benzene in the C -C fraction is being alkylated by isobutylene to give alkyl aromatic material boiling much higher than hexane. The 310 cc. of hydrocarbon product resulting from the alkylation is fractionally distilled to give 38 cc. of a hexane product boiling between 65 C. and 75 C. at 760 mm. and containing 0.24% benzene. This final product is suitable for use as commercial hexane.

EXAMPLE III A sample of rafiinate boiling up to 228 C., obtained by selectively extracting aromatics from a Platformer by selectively extracting aromatics from a Platformer product with 2-hydroxyethyl dimethyl carbamate containing about 5% of water, is fractionally distilled to obtain about 7.0% of a C -C hydrocarbon fraction containing about 1.4% toluene and 0.7% benzene. A mixture of 150 cc. of this C C fraction and cc. of hydrofluoric acid is stirred under atmospheric pressure at about 10 C. while a mixture of equal volumes of isobutane and isobutylene is passed therethrough. Here again, while the normal alkylation reaction is occurring between isobutane and isobutylene, much of the benzene in the C -C fraction is being alkylated by isobutylene and portions of the toluene are being alkylated to alkyl aromatic hydrocarbons boiling much higher than the hexane and heptane. The 300 cc. of hydrocarbon product resulting from the alkylation is fractionally distilled to give about 15 cc. of hexane fraction boiling between 65 C. and 75 C. at 760 mm. and containing 0.11% benzene as one fraction and about 18 cc. of a heptane fraction boiling between about 75 C. to 100 C. at 760 mm. and containing 0.13% toluene. These final fractions are suitable for use as commercial hexane and commercial heptane fractions, respectively.

The reforming operations taking place in reformer 12 are conventional. Various catalytic reforming operations and processes are suitably employed in the practice of this invention. Suitable reforming processes may be sufficiently described and identified to those skilled in the art by their descriptive names which are generally known and used and licensed throughout the petroleum industry. Accordingly, catalytic reforming processes applicable in the practice of this invention include, but are not limited to Catforming, Catalytic Reforming, Houdriforming, Ultraforming, Platforming, Cycloversion, Fixed Bed Hydroforming, Fluid Hydroforming, Hyperforming, Thermofor Catalytic Reforming, or Savaforming and the like. These catalytic processes are generally and specifically described in the literature and patents relative thereto. These catalytic processes have as their objectives the upgrading of relatively low-grade or low-octane naphthas or petroleum fractions in the gasoline boiling range, or naphthas generally, to higher-octane motor gasolines. Such a product is removed from the instant process at lines 14 and 20. These processes also have as their objectives the production of high-octane motor-fuel components from naphthas or selected petroleum fractions, or the production of high yields of aromatics, petrochemicals, or hig quality motor-fuel components. Such a product or products are removed from either lines 32 or 14 in the instant process and do not constitute the primary objective of this invention. In these processes the separation of components, particularly by solvent extraction, produces a predominantly paramnic productwhich is the primary source of the C C 'paraffinic product of this invention.

The catalytic reforming reaction taking place in reformer 12 may be carried out by employing a fixed bed of catalyst, a'moving bed of catalyst, a catalyst in fluidized condition, or any of the various combinations of these processes carried out in a single reaction zone or a plurality of reaction zones. The conditions of operation are well known. The temperature may range from about 700 F. to 1050 F. and preferably is about 850-1000" F., and the pressure may vary from about 150 to 1000 p.s.i.g., with 200 to 750 p.s.i.g. preferred, depending on the severity of reforming desired and on the composition of the naphtha charge entering at line 10.

The numerous catalyst compositions known in the art to attain these objectives may be used, e.g., chromiaalumina catalysts, platinum-containing catalysts, molybdena-alumina catalysts, and cobalt molybdate catalysts. Cycloversion over bauxite at 9504000 F. and 50-60 p.s.i.g.,Hydroforming over MoO /Al O at 900 F. and 150 p.s.i.g., Platforming over Pt/Al O at 900 F. and 750 p.s.i.g., Fluid Hydroforming over MoO /Al O at 890-940 F. and 200 p.s.i.g., and Ultraforming over Pt/ A1 at 900950 F. and 200-500 p.s.i.g. are non-limiting examples. The foregoing processes mentioned generally or specifically simultaneously accomplish to various degrees such reactions as aromatization or dehydrocyclization, dehydrogenation, isomerization, disproportionation along with some cracking taking place depending on the severity of the'treatment and the nature of the naphtha; feed. Dehydrogenation converts naphthenic hydrocarbons to aromatics, and isomerization converts mparafiinic hydrocarbons to isoparafiinic hydrocarbons; these are further converted to the corresponding aromatic hydrocarbons. A preferred reforming catalyst comprises platinum or palladium supported on alumina or on a siliceous craclc'ng catalyst. Such catalysts are well-known in this art and contain about 0.1 to 1.0% by weight of platinum or palladium on the selected support. These catalysts and their preparation are described in anumber of US. patents, e.g., 2,705,329; 2,589,189; 2,550,531; 2,479,109, and 2,478,916. About 0.1 to 0.8% of fluorine or chlorine as combined halogen based on the support may be incorporated, if desired. The manner of preparation is in accordance with conventional techniques of impregnation of the selected support, e.g., alumina, silica-alumina, silicazirconia, silica-alumina-zirconia, etc., with an aqueous solution of chloroplatinic acid or chloropalladic acid, or with an aqueous solution of the ammonium salts of these acids. After impregnation, the support is dried at about 210 to 250 F. and reduced with hydrogen at about Following the catalytic reforming operation, the resulting liquid reformate in line 14 is subjected to some form of separation, i.e., by absorption, solvent extrac tion, etc., to separate a predominantly aromatic fraction at line 32 and a predominantly paraiiinic fraction at line 9 34-. The preferred method of separation is by'means of solvent extraction, i.e., liquid-liquid contact with a selective solvent which selectively dissolves the aromatic hydrocarbons and leaves an undissolved rafiinate of parafiinic hydrocarbons. The raflinate-in line 34 is subjected to washing or distillation to remove the small portions of solvent, prior to entry into line 40. Thus the raffinate may be sent through a still and a solvent-free rafiinate produced, which is sent to line 40. Since this treatment is well-known, it is not shown in the drawing. In some instances, where the solvent is inert, present in very small quantities, and is not affected by the alkylation reaction, solvent separation from the rafiinate is unnecessary.

Selective solvents suitable for use in extraction tower 16 include the well-known selective solvents for aromatics, e.g., diethylene glycol, triethylene glycol, tetraethylene glycol, monopropylene glycol, dipropylene glycol, tripropylene glycol, mono-, diand tri-butylene glycols, phenol, sulfur dioxide, nitrobenzene, furfural, Chlorex, 2-hydroxyethyl dimethyl carbamate, and others. Also suitable as selective solvents are the 'polyoxypolyalkylene glycols, the glycol ethers, such as the Cellosolve series of compounds, alkyl ethers of ethylene glycol, including methyl-Cellosolve, ethyl-Cellosolve, proply-Cellosolve, and butyl-Cellosolve. Compounds known as Carbitols, which are alkyl ethers of diethylene glycol, such as the methyl-, ethyl-, propyl-, and butyl-Carbitols, the glycol and polyoxypolyalkylene glycol esters of low-molewt. organic acids, such as acetates and 'propionates, may be used. These solvents may be used alone, in admixture, and in aqueous solution. The Udex extraction process described in the Petroleum Refiner, vol. 31, No. 9, Sept. 1952, p. 246, employing a diethylene glycolwater solvent containing about 2 to 10% of water, is the preferred method of separation and is used to illustrate the invention. The objectives of this step of this invention are met by using any of the foregoing or other known solvent-extraction process, and by using a solvent having a relatively high boiling point and low vapor pressure as compared with the aromatic and/or nonaromatic hydrocarbons in the reformate.

The alkylation reaction taking place in reactor 42 is carried out using conventional techniques. For this purpose, the desired ratio of saturated hydrocarbon entering line 36 and olefin hydrocarbon entering line 38 is contacted with an alkylation catalyst which may be sulfuric, phosphoric, or hydrofluoric acid, or any other agent having the property of promoting the alkylation reaction. Theconditions of operation in alkylation unit 42 are well known and include temperatures in the range of about 10 to F., using pressures in the order to 25 to 150 p.s.i.g., and about 0.05 to 0.2 mole of catalyst per mole of alkylation hydrocarbon mixture. The alkylation reaction, wherein saturated'parafiinic hydrocarbons are combined directly with olefinic hydrocarbons to produce higher-molecular-Weight hydrocarbons of a generally saturated character, is conducted in alkylation reactor 42. In the sulfuric acid alkylation process, which is used to illustrate the instant invention, a charge comprising one or more isoparafiinic hydrocarbons such as isobutane, and one or more olefinic hydrocarbons, including isobutylene, is contacted with sulfuric acid, generally concentrated sulfuric acid having a concentration of about 90% to at temperatures of 10 to 80 F., and at pressures up to 30 pounds per square inch. To prevent polymerization of the olefins, particularly when sulfuric acid is used as the catalyst, it is generally necessary to maintain a low concentration of olefinic reactant in the charge. The temperature used is limited by dealkylation and/or degradation of the hydrocarbon product to low-molecular-weight hydrocarbons and by the occurrence of side reactions, including polymerization of the olefinic reactant. This is particularly true where sulfuric acid is the catalyst. In

general, the acid catalyst such as sulfuric acid is used in an amount varying between about 10% and 100% by weight, based on the total weight of reactants charged at line 40.

Other alkylation processes, such as with the use of mercuric aluminum bromide or antimonous aluminum bromide at 750 pounds per square inch pressure and a temperature of 100 to 200 F., may be used. The technique of using boron fluoride promoted with methyl butene and water or hydrogen chloride may also be used. Similarly, aluminum chloride or a concentrated sulfuric acid catalyst containing a mercury compound and a selenium compound may be used.

One method that is applicable is described in US. Patent 2,435,761 wherein a C4-C7 paraffinic hydrocarbon such as isobutane is reacted with olefins such as butylenes using boron trifluoride promoted with chlorine or bromine. The employment of a gaseous mixture of isoparaffins and olefins with small particles of liquid hydrofluoric acid, at a temperature above the normal boiling point of hydrofluoric acid and at a pressure slightly above the critical pressure of the acid to allow its subsequent vaporization and consequent cooling of the reaction mixture, as described in US. Patent 2,437,544, may also be used. The catalyst may be bromine and carbon tetrachloride, carbon tetrabromide, chloroform, or bromoform in accordance with US. Patent 2,468,899. Regardless of the process applied in alkylation unit 42, the objectives of this invention will be obtained as long as the lower-boiling portion of the product in line 48' predominates in paraflinic hydrocarbons having 6 to 8 carbon atoms per molecule, and particularly if this alkylation product predominates in hexane or paraffins boiling in the hexane boiling range.

The last step of the process comprises a distillation carried out in still 50 designed to separate the alkylate as a bottoms fraction and the aromatic-free naphtha, as the primary product of this invention, is drawn off at line 54. In this process an overhead temperature of about to 32 F. and pressures ranging from about 20 mm. to 740 mm. Hg are used. An overhead com prising unreacted parafiinic and olefinic hydrocarbons is removed by line 56 and recycled to line 40.

The spent acid Withdrawn from line 46 is reconsti tuted by known methods and recycled to the alkylation unit.

Having thus described the invention with non-limiting examples the only limitations attaching thereto appear in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. The process of preparing parafiinic hydrocarbons boiling in the range of about 49 to 100 C., and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C to C parafiinic and naphthenic hydrocarbons to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to solvent extraction using a solvent selective for the aromatic hydrocarbons present, recovering a rafiinate phase rich in parafiinic hydrocarbons, subjecting said rafiinate to alkylation in the presence of an alkylatable hydrocarbon mixture, and fractionating this resulting alkylated mixture to obtain at least one fraction boiling in the range of about 49 to 100 C. having a content of aromatic hydrocarbons of less than about 0.5 by volume.

2. The process of preparing paraflinic hydrocarbons boiling in the range of about 49 to 75 C. and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C parafiinic and naphthenic hydrocarbons to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to solvent extraction using a solvent selective for the aromatic hydrocarbons present,

recovering a raftinate phase rich in paraflinic hydrocarbons, subjecting said raflinate to alkylation in the presence of an alkylatable hydrocarbon mixture, and fractionating this resulting alkylated mixture to obtain at least one fraction boiling in the range of about 49 to C. having a content of aromatic hydrocarbons of less than about 0.5% by volume.

3. The process of preparing parafiinic hydrocarbons boiling in the range of about 75 to C., and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C C parafiinic and naphthenic hydrocarbons to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to solvent extraction using a solvent selective for the aromatic hydrocarbons present, recovering a raffinate phase rich in parafiinic hydrocarbons, subjecting said rafiinate to alkylation in the presence of an alkylatable hydrocarbon mixture, and fractionating this resulting alkylated mixture to obtain at least one fraction boiling in the range of about 75 to 100 C. having a content of aromatic hydrocarbons of less than about 0.5 by volume.

4. The process of preparing parafiinic hydrocarbons rich in hexane and boiling in the range of about 49 to 75 C., and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C parafiinic and naphthenic hydrocarbons to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to solvent extraction using a solvent selective for the aromatic hydrocarbons present, recovering a raffinate phase rich in paraffinic hydrocarbons, subjecting said rafiinate to alkylation in the presence of an alkylatable hydrocarbon mixture, and fractionating this resulting alkylated mixture to obtain at least one fraction rich in hexane boiling in the range of about 49 to 75 C. having a content of aromatic hydrocarbons of less than about 0.5% by volume.

5. The process in accordance with claim 4 in which said recovered fraction predominates in hexane and contains about 0.38% by volume of benzene.

6. The process of preparing paraffinic hydrocarbons rich in heptane and boiling in the range of about 75 to 100 C., and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C paraffinic and naphthenic hydrocarbons to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to solvent extraction using a solvent selective for the aromatic hydrocarbons present, recovering a raffinate phase rich in paraflinic hydrocarbons, subjecting said ralfinate to alkylation in the presence of an alkylatable hydrocarbon mixture, and fractionating this resulting alkylated mixture to obtain at least one fraction rich in heptane boiling in the range of about 75 to 100 C. having a content of aromatic hydrocarbons of less than about 0.5% by volume.

7. The process in accordance with claim 5 in which said recovered fraction predominates in heptane and contains about 0.24% by volume of toluene.

8. The process of preparing parafiinic hydrocarbons boiling in the range of about 49 to 75 C. and having a content of aromatic hydrocarbons of less than about 0.5% by volume, which comprises reforming a naphtha rich in C paraffinic and naphthenic hydrocarbons at a temperature of about 70 to 1050 F. and a pressure of about to 1000 p.s.i.g. in the presence of a platinumcontaining catalyst to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to contact with a solvent comprising diethylene glycol and water, separating a raffinate phase rich in parafiinic hydrocarbons, subjecting said raffinate to alkylation in the presence of concentrated sulfuric acid and an alkylatable hydrocarbon mixture comprising isobutylene and isobutane to produce an alkylate reaction product, and frac- 9 tionating the alkylate reaction product to obtain at least one fraction boiling at about 68 C. comprising substantially pure hexane and having a content of aromatic hydrocarbons of less than about 0.5% by volume.

9. The process of preparing parafiinic hydrocarbons boiling in the range of about 75 to 100 C., and having a content of aromatic hydrocarbons of less than about 0.5 by volume, which comprises reforming a naphtha rich in C parafiinic and naphthenic hydrocarbons at a temperature of about 70 to 1050 F. and a pressure of about 150 to 1000 p.s.i.g. in the presence of a platinumcontaining catalyst to form a reformate, stabilizing the reformate, subjecting the stabilized reformate to contact with a solvent comprising diethylene glycol and water,

separating a raflinate phase rich in paraffinic hydrocar- 15 3050456 bons, subjecting said raflinate to alkylation in the presence of concentrated sulfuric acid and an alkylatable hydrocarbon mixture comprising isobutylene and isobutane to produce an alkylate reaction product, and frac tionating the alkylate reaction product to obtain at least one fraction boiling at about 100 C. comprising substantially pure heptane and having a content of aromatic hydrocarbons of less than about 0.5% by volume.

References Cited in the file of this patent UNITED STATES PATENTS 2,865,837 Holcomb et a1. Dec. 23, 1958 2,933,445 Donnell et al. Apr. 19, 1960 Melchior Aug. 21, 1962 

1. THE PROCESS OF PREPARING PARAFFINIC HYDROCARBONS BOILING IN THE RANGE OF ABOUT 49* TO 100* C., AND HAVING A CONTENT OF AROMATIC HYDROCARBONS OF LESS THAN ABOUT 0.5% BY VOLUME, WHICH COMPRISES REFORMING A NAPHTHA RICH IN C6 TO C8 PARAFFINIC AND NAPHTHENIC HYDROCARBONS TO FORM A REFORMATE, STABILIZING THE REFORMATE, SUBJECTING THE STABILIZED REFORMATE TO SOLVENT EXTRACTION USING A SOLVENT SELECTIVE FOR THE AROMATIC HYDROCARBONS PRESENT, RECOVERING A RAFFINATE PHASE RICH IN 